1. Field of the Invention
The present invention relates to an apparatus for continuous polymerization to be used for manufacturing a methacrylate-based polymer and the like, and a method for continuous polymerization using the same.
2. Description of the Related Art
In recent years, a continuously bulk-polymerizing method and a continuously solution-polymerizing method for continuously adding monomers and a polymerization initiator into a polymerization reaction vessel to polymerize the monomers have been adopted for manufacturing a methacrylate-based polymer, an acrylate-based polymer, polystyrene, acrylonitrile-butadiene-styrene resin (ABS) and the like. Among these, the continuously bulk-polymerizing method has the advantage of obtaining a polymer with fewer impurities due to the polymerization reaction in a homogenous phase without using a solvent, a dispersing agent and the like. However, the viscosity of its reaction mixture is extremely high, so that the heat removal of the reaction system and the control of polymerization temperature are difficult. The continuously solution-polymerizing method also has the advantage of obtaining a polymer with fewer impurities, while the heat removal and control of polymerization temperature are relatively easy. However, its productivity tends to be reduced due to a solvent to be used therein.
In addition, Japanese Patent Publication No. 3395291 discloses a method of manufacturing a methacrylate-based polymer by a continuous bulk-polymerizing method in which a polymerization reaction is conducted using a complete mixing-type reaction vessel in an adiabatic state of no substantial comings and goings of heat from outside as well as in a flooded state of no substantial gas phase portion in the reaction vessel during the reaction.
A lot of methods for heat removal of a reaction system have conventionally been known, such as a cooling system by heat transfer in which a reaction system is cooled down using a jacket provided at an outer wall surface of a reaction vessel and a coil disposed in the reaction vessel; and a so-called reflux cooling system in which a raw material monomer and the like are vaporized in a reaction vessel and is taken out of the reaction system to be condensed by cooling and returned again to the reaction system. In the conventional heat removals, cooling may be localized or be conducted abruptly.
In manufacturing a methacrylate-based polymer, such local and/or abrupt cooling of a reaction system tends to cause gel to attach and grow at an inner wall surface of the reaction vessel, which may leads a gelated product contaminated into a polymer produced.
Conventionally, in manufacturing a methacrylate-based polymer, a raw material monomer and a polymerization initiator may be previously mixed and dissolved so that the polymerization initiator has a predetermined concentration, and then be supplied to a reaction vessel. In adopting the manner of a method described in Japanese Patent Publication No. 3395291, the performance of a polymerization reaction in an adiabatic state as well as in a flooded state may prevent from generating gel to attach to an inner wall surface of a reaction vessel due to the localized or abrupt cooling. Still, this method described in Japanese Patent Publication No. 3395291 has a possibility of causing dispersion in quality of the resulting polymer. This is because in order to maintain an adiabatic system in this method, the temperature of a jacket is controlled to be the same temperature as that in the reaction vessel depending on the fluctuation of the temperature in the reaction vessel, and the raw material monomer is previously prepared so as to contain a polymerization initiator at a predetermined concentration, and thus when polymerization temperature fluctuates with a factor of, such as, the change in outside air temperature, a later polymerization temperature and the temperature of the jacket can fluctuate freely.